Revert "Set RETRO_ENVIRONMENT_GET_SAVE_DIRECTORY to g_settings.system_directory if a SAVE directory hasn't been set"

This reverts commit d9910a6eb608d5cdf80d5e365e1ab1250f55973b.
Revert "Revert "Set RETRO_ENVIRONMENT_GET_SAVE_DIRECTORY to g_settings.system_directory if a SAVE directory hasn't been set""
This should be handled by the core

This reverts commit b20ece69ed18196cdd330d2379c994858b78771e.